Clamp for printing press plates



Jan. 29,1946. rw. Mm BARK'ER' 2,393,878

CLAMP FOR PRINTING PRESS PLATES v Filed Dec, 2, 1944 M 2 sheets-sheet 1ATTOENEY Jan. 29, 1 946. w. Macv. BARKER 2,3935878 CLAMP FOR 'PRINTINGPRESS PLATES rFiled Dec. 2, ,1944 2' sheets-sheet 2 INVENTOR, wfm/E MQ MBAE/ 52 BY tion to produce Patented Jan. 29, 1946 'l UNITI-:o STATESPATENT OFFICE i y CLAMP FORPRINTING 'Panes VPLATES Wayne MacVeaghBarker, Philadelphia, Pa. AApplication December 2, 1944, SerialNo.566,326

` claims (o1. 101e-,378)

In,- the art of printing, it is now customary to cast the type and cutsto be used in the form of 'curvilinear plates which are detachablyfsecured to a supporting rotary press cylinder by clamps movable in'circumferentially spaced, .longitudinal grooves and engaging theopposite vertical edges of the plates, means being provided foractuating said clamps into orout ofengage'- ment with said plates.

In operation, the highspeed rotation of the press cylinderproducescentrlfugal force of such intensity that the center portions ofthe plates tend to buckle or bulge away from the surface of the presscylinder. This withdraws .theA vertical ledges of the plates awayr fromthe clamps. If, as a result, the edges of a plate are completelydisengaged from the securingclamps, the entire press may be seriouslydamaged. Y

It is, therefore, one object of my invention to produce an improvedclamp construction by means of which the danger of damage due todisengagement of a plate from the securing clamps is considerablyreduced or eliminated.

In use, the supporting cylinder carrying Vthe plates rotates in constantpressure against a contact cylinder. Therefore, the plates which arebulged or buckled by centrifugal force will be violently pushed backagainst the supporting cylinder by the contact cylinder with eachrevolution of the plate supporting cylinder. This re'- sults in poundingof the press plate against the supporting cylinder'. y

It is, therefore, a furtherobiect of my invention to produce an improvedclamp construction and assembly by which the shock resulting from thepounding action referred' to is effectively absorbed.

Like other parts, the clamps are subjecty to wear and, due to theirexpense, they may not be readily discarded and replaced. y

It is, therefore, a further object of my invenan improved yclamp whichwill operate satisfactorily even after a relatively great amount of wearhas developed.

A still further object is to devise an improved arrangement whereby theclamps may be removed from the grooves in which they operate, withminimum dismantling or disturbance of other coacting parts.

A still further object is to devise an improved arrangement by means ofwhich Vthe `wearing strips usually provided between the clamps and thegrooves in which they move, may be removed and replaced withoutdismantling any other parts.

A still further object is to produce an improved structure `in which thetendencyof centrifugal force to` throw outthe lubricant usually usedbe-v tween the clamps and the wearing strips and the walls of thegrooves in which they move is greatly reduced. 1 f

These andother objects are effected by my -invention as will be`apparent from the v4following description and claims taken inconnection with the accompanying drawings, forming a part of thisapplication, in'which: Y y Y,

Fig. 1 is a fragmentary top plan view ora `rotary press cylinder of aconventional printing press, such as the Hoe press,V towhich my novelclamp is applied; f Y

Fig. 2- is a fragmentary, longitudinal vertical section taken along line2-2 of Fig. V1 ori4. showing a portionof a press cylinderuwith pressplates clamped in operating position;

Fig. 3 is a view similar to Fig., 2, with the press plates removed; 1

Fig. 4 is an enlarged vvertical section on line 4-4 of Fig. 1;

Fig. '5 is an enlarged view of a portion of Fig. 4, showing theapparatus when not in operation;

Fig.k 6 is aview similarto Fig. 5,showing the parts when the cylinder isrotating; and Y Fig. 7 isa fragmentary top plan view showing themannerin which the clampsections embodying my invention may be withdrawnfrom,V the grooves in which they move. v f

Referring-to the drawings in which like reference characters indicatelike parts, lo designates a rotary cylinder 4of a conventional presssuch as the well known Hoe printing press, only lslightly more thanone-half of the cylinder being shown. The cylinder I0 is provided with anumber of equally spaced, dovetailed groovesl! which extendlongitudinally of the cylinder, as clearly shown in Figs. 1 and 4. InFig. 4, I have shown six of these grooves, but it is to beunderstoodthatthe number of grooves forms no part ofthe presentinvention. Thegrooves. l2 open at their upper end into dovetaile'xil recesses I4 whichare' coextensive with the grooves. The cylinder Il) is provided atabutment I5 which projects beyond the ciroum ference of the cylinder andwhich is provided with oppositely beveled edges lil.y The abutment I6divides the cylinder into two identical halves,

only one of which is shown and described.

As shown, the cylinder is adapted tojcarry two or more curvilinearplates 20'a'nd 22, which carry the desired type and cuts, and which aredetaclijA ably clamped to the cylinder by means of clamps its centerwith a fixed annular A'and B movable in the grooves I2.Y The verticaledges ofV the plates 20 and 22 are beveled, as

clearly seen in Fig. 2-.

As will be seen from Figs. l4 to 6, the grooves I2 and recess I4 areboth. of a dovetail shape,-but

they are disposed in apposition, with the tapered or Vnarrow portionsthereof contiguous. The clamps Aan'd B are also shaped to fit thegrooves and recess. clamp is'made of twosimilarsections each of Y whichincludes a lower enlarged Yportion 28 4and an enlarged upper portion 30,the portions 28 and Ascan be seen in Figs. 4 t06, each in Fig. 3. New

30 being connected by a reduced portion 3| and seating in the groove I2and recess I4, ,respectively. It will be noted that the center ofgravity of each clamp s ection is located at the point X inthelowerenlarged portion. 28 thereof. The upper portions 30 of the clamps `A andB are providedwith abutments32 and 34, respectively, which ,exf

tend beyond theV circumference of the cylinder and the press platescarried thereby, as best seen Y -in Fig. 2. The abutments34 of the clampsections B are provided with oppositely beveled redges 36 and 38 toengage the adjacent-edges of the plates 20 and 22,^the inner edge of theplate 20 being engaged by the beveled edge I8 of the central abutmentVI6. Theabutments 32 of the clamp sections A are provided with onebeveled edge 40 Ywhich engages the outer edge of the plate 22. The'lowerportions 28 of the clamp sections A or B are recessed so as 5to form abore 42 through which the shafts actuating the clamps A and B pass.VVEach of the clamps B is actuated by a shaft 44 passing through the bore42 and carrying adjustable nuts or stop collars 46-and 48.

VThe inner end 'of the shaft 44is adapted to enter a bore 50'formed in afixed block 52'or in a part of the cylinder.y The outer rreduced end ofthe shaft 44 is adapted to enter a bore54 in a block 56 freely movablein the groove I2. The shaft 44 Operation the shafts 6 to the right,asrviewed in Fig. 2, against the action of the spring 10. Thisenablesthe Vsprings 50 to push the shafts 44 and blocks 56 to the right also.In this position, A and B are also in their extreme right-handpositions, in'which the beveled edges 36, 38 and 40 are out ofengagement with the edges of the adjacent plates and' 22, which `maynowl be removed. The parts will now'a'ppear as shown plates can now soonas the lockingand actuating arm is released,

the spring ,'Iwill 'return the parts to the position shown in Fig. i2,in

22 are tightly clamped.

As the cylinderrotates due to centrifugalforce,

which the plates 28 and at high speed, the plates,

' as shown'in a greatly exaggerated manner Vby the is normally biasedoutwardly, orto therightas viewed in Fig. 2', by a spring 58 seated inthe bore 5I).V 'Y Y f Each of the clamps A is actuated .by ashaftrpassing through the bore 42 in the clamp and carrying adjustable nuts orstoprcollars 62 and 64. The' inner end of the shaft 60 is reduced and isadapted to enter the other end 4of the bore 54 of the movable block 56.YNear its other end, the shaft 6U carries a xed collar 66 and a movablecollar 68 between which is confined a spring 10. The spring I0 isstronger thanthespring V58 and biases the shaft 60 inwardly or to theleft of Fig. 2. The outer end l2 of the shaft 6I)V detachably engages aslot 'I4 in a bracket 16. An actuating and locking arm (not sh'ovvn)moves the lshafts 60 outwardly, or to the rightas viewed in Fig. 2,against the action of the spring 18. fThe actuatf ing arm'referred toand the means by which movement of saidV arm -is transmitted to saidshafts are conventional and'hence not shown nor described. It issuiicient to statethat the actuating arm moves all Ythe sh'afts 60,around the entire circumference of the cylinder, simultaneously, andthat said arm is not directly secured to the shafts 60 themselves.Between theclamp sections and the walls of the grooves I2 are interposedwear-v ing strips 80 w ch are retained in position by externallyaccessible dog screws 82, the heads of which are countersunk as shown inFigs. 5 and 6. By reference to Fig. 5, it will also be noted that aporting shaft, can then vas described, the shafts dotted lines in Fig.2'. clamps A and B, under will be moved axially of contact with theedges venting the plates from the machine.

Whenv this happens, the action of thels'pring 10, the cylinder .tomaintain of the plate,V thus preflying off and wrecking As the cylinderrotates in contact with a pres-f sure cylinder, not'shown, thebulged'plates 20`and 22V are pressed back against the cylinder-"I0, thusy producing a reciprocating pounding action against Y thev clamps A andB. This action'produces `wear along the contacting faces' ofthe wearingstrips, the wear beingA naturally greater on the wearing strips than onAvthe faces of theV clamps. In order to remove the strips forreplacement, it is merely necessary to disengage the dog screws 82 andthen move the strips longitudinally ofthe grooves until they clear thecorresponding clamp sections, as sh'own in Fig. '7. The strips may nowbe pulled out from the grooves I0 and replaced with new ones without inany Way vdisturbing the rest of the assembly.

To remove the clamp sections from the grooves,

the sections ofthe clamps gitudinally untilr they clear ing strips, asshown in Fig. 7. The clamp sections on each shaft 60, together withtheir supbe pulled out of their respective grooves, the shafts vhavingbeen rst disengaged from the `bores 54 and the vslots 14. With theshafts 68 andthe clamps Aremoved, the shafts 44 are disengaged from thebores 50, and, with the sections of the clamps B staggered yA arestaggered lonbe removed out/of their respective grooves. l The clampsections 28 fit snugly inthe grooves I2, only enough .clearance beingprovided to permit ready sliding of the clamps linthe grooves. Suchclearance is represented at 43 in Fig. 5. When the cylinder Vis rotated,the clamps are subjected to centrifugal force Ywhich moves them radiallyoutwardly until stopped by the wearing strips. During their initialradial movement, the

abutting faces of the clamp sections arc parallel and slightly spacedand when the clamp sections first abut their respective wearing strips,the?,l

contact the strips valong their yentire area. ThisV Y is the expectedresult ofthe centrifugal force ditions, that the wearing strips actingon the clamp sections. However, VI have found by observation of wearstrips used in a cylinder made according tothe invention and actuallyrun and used under actual working con first 'show signs of Yimpact andwear along theportions thereof immediately inwardly of the points D.From this the clampsV be putin and, as

tend to bulge outwardly,

clamps and the their respective wear- 44 and the clamps Bmay I assumethat, as the cylinder rotates, the ,clamp sections intermittently assumethe position'shown in Fig. 6 which is the only position consonant withthe signs of impact and which develope on the wearing strips, first, andultimately on the corresponding portions of the abutting faces of theclamp sections. While I am not able to determine exactly what takesplace, I believe this result is due to the location of the center ofgravity of the clamp sections with reference to the wear strips and thereduced opening formed at the junction of the grooves l2 and I4. Bycalculation, it can be seen that the center of gravity of the clampsections is at about the point X or spaced inwardly and laterally fromthe points D. Due to the fact that the combined cross sectional width ofthe inner portions of the clamp sections is greater than the width ofthe opening measured along a line connecting the points D, and becausethe center of gravity of the left-hand clamp section, for example, is atX, or to the right, as viewed in Fig. 5, of a radius passing through thepoint D of the wearing strip of this clamp section, 'the centrifugalforce will, after the clamp section has moved outwardly into abutmentwith its wearing strip, impose a turning moment (in counterclockwisedirection) about the point D thus causing the clamp section to rotate aslight extent in counterclockwise direction. Similarly, and for the samereasons, centrifugal force imposes on the right-hand clamp section aturning moment in clockwise direction. The rotation of the clampsections in opposite directions causes two clamp sections to abutagainst each other at E. The rotative movements produce invertedV-shaped clearances between the lower portions of the wearing strips 80and the clamp sections 28, as indicated to an exaggerated extent at F inFig. 6, and also V-shaped clearances between the upper portions oftheclamp sections, as indicated to an exaggerated extent at C in thesame figure.

The rotation of the clamp sections about the line or point D causes theouter end portions 35 of its abutments 34 t'o be drawn radially inwardlyagainst the plate 20 or 22 to hold the same firmly against the cylinderI0. This turning moment thus causes the outer end portion of theabutment constantly to bear radially inwardly against and to clamp theplates 20 or 22 against the cylinder.

It will be noted that the shafts 44 of the clamps B are held relative tothe cylinder by the blocks 52 and 5B, and that there is sufficientclearance between the shafts and the bores 42 so that the surfaces ofthe bores 42 never touch the shaft. On the other hand, the inner ends ofthe shafts 60 of the clamps A are held at one end by blocks 56, but theouter ends of these shafts are movable in the slots 14. The outer endsof the shafts 60 are, in eiect, held by the clamps A and the clearancebetween these shafts and the bores of the clamps A is sufficient only topermit free sliding. In operation, therefore, the centrifugal force ofthe shaft is imposed on the clamps A and increases the turning momentexerted on the clamps A. In other respects, the scheme of operation ofthe clamps A is the same as that of the clamps B.

What I claim is:

1. In a printing press including a cylinder adapted to support a curvedimpression plate,

means for locking said plate in position including a clamp formed of twocomplementary, identical sections, each of said sections having an outerportion, an inner portion and an arcuate abutment carried by each ofsaid outer portions and projecting beyond the circumference of thecylinder for engaging the curved edge of said plate, said abutmentsbeing parallel to the circumference of said cylinder when said cylinderis stationary, the juxtaposed faces of said clamp sections being flatand normal to a horizontaly plane passing through the axis of rotationof said cylinder, there being complementary arcuate recesses in saidflat faces which, when said clamp sections abut each other, form a boredisposed parallel to the axis of rotation of said cylinder andsubstantially centrally of said clamp, there being a groove formedlongitudinally of said cylinder and having an outer portion for seatingthe outer portions of said clamp sections and an inner portion forseating the inner portions of said clamp sections, the outer portion ofsaid groove being defined, in part, by converging walls sloping from thesurface of the cylinder toward a line passing through the center of thegroove and normal to the axis of rotation of said cylinder, and theinner portion of said groove being defined, in part, by diverging wallsbeginning at the lower ends of said converging walls and sloping awayfrom said line, the width of said groove at the junction of saidconverging and diverging walls being less than the width of either theouter or inner portion of said groove, the walls of said clamp sectionsbeing shaped to provide surfaces parallel to said converging anddiverging walls, respectively, whereby a reduced portion is producedbetween the inner and outer portions of said clamp sectionscorresponding to, and registering with the reduced width portion of saidgroove formed at the junction of, said converging and diverging walls,and means for actuating said clamp into and out of engagement with saidplate including a shaft extending through said bore, means for engagingsaid shaft with said clamp for joint movement, and means for actuatingsaid shaft and said clamp longitudinally of said cylinder.

2. The structure recited in claim 1 in which said cylinder is providedwith a plurality of grooves and a plurality of clamps in said grooves,together with means for actuating each of said clamps.

3. The structure recited in claim 1 in which the width of the groove, atits restricted portion, is greater than the width of the inner portionof one of the clamp sections, but is less than the total width of theinner portions of a pair of sec-v tions constituting a complete clamp,and in which said clamp sections are movable longitudinally of eachother whereby said clamp sections may be removed singly, transversely ofsaid groove.

4. The structure recited in claim 1 together with wearing strips betweenthe diverging walls of the groove and the corresponding portions of theclamp sections, and externally operable means for securing said stripsto said walls, whereby said strips may be secured to, or disengaged fromsaid walls and removed from the groove without removing said clamp orsaid shaft from said groove.

WAYNE MACV'EAGH BARKER.

